Interleukin-5 modulates eosinophil accumulation in allergic guinea pig lung.

Based on its involvement in eosinophil biology, interleukin 5 (IL-5) may play a role in the pulmonary eosinophilia associated with allergic reactions. We have examined that hypothesis using a neutralizing antibody to IL-5 in ovalbumin-sensitized guinea pigs challenged with aerosolized antigen. The extent of eosinophilia has been quantitated in bronchoalveolar lavage (BAL) and by histologic evaluation of lung tissue sections. Acute intraperitoneal administration of a rat IgG, monoclonal antibody to murine IL-5 derived from TRFK-5 cells prevented lung and BAL eosinophilia in a dose-dependent fashion at and above 10 micrograms per guinea pig. Treatment with either an experimentally irrelevant, isotype-matched antibody from GL113 cells or with heat-denatured IL-5 antibody was without effect. These studies demonstrate the importance of IL-5 to pulmonary eosinophilia in challenged, allergic guinea pigs.

Anaphylactic challenge causes eosinophil accumulation in bronchoalveolar lavage fluid of guinea pigs. Modulation by betamethasone, phenidone, indomethacin, WEB 2086, and a novel antiallergy agent, SCH 37224.

Eosinophil infiltration into bronchoalveolar areas of the lung has been assessed in guinea pigs sensitized to ovalbumin (OA) and then challenged with the aerosolized antigen. Cell content, histamine, and guinea pig albumin (GPA) have been measured in bronchoalveolar lavage (BAL) fluid from these animals. Extensive eosinophil accumulation resulted from sensitization followed by OA challenge; monocytes that initially accounted for greater than 80% of the BAL cells remained essentially constant, and neutrophils comprised less than 3% of the population throughout. Eosinophils were elevated at 3 h, peaked with a fivefold increase at 24 h, and remained elevated for at least 7 days. Histopathologic changes observed in lungs taken from sensitized guinea pigs 24 h after OA challenge confirm this eosinophilia. Increased histamine and GPA were detected only at 5 min. Oral treatment with betamethasone (ED50 = 0.4 mg/kg), phenidone (ED50 = 15 mg/kg), Sch 37224 (ED50 = 0.5 mg/kg), and WEB 2086 (ED50 = 4 mg/kg) decreased eosinophil accumulation in the BAL fluid, indicating roles for 5-lipoxygenase products and PAF in this multimediator-dependent model of allergic inflammation. On the other hand, 4 mg/kg of indomethacin increased total cells with no effect on eosinophils, precluding a major role for cyclooxygenase products. Sch 37224, an antileukotriene agent and an orally active novel antiallergy agent in sheep, guinea pigs, and humans, is as potent as betamethasone at blocking eosinophil infiltration, suggesting that it may also suppress human pulmonary inflammation.

The role of a Ca2+/calmodulin dependent plasma membrane Ca2+ channel during concanavalin A activation of MC9 mast cells.

The effects of Con A on free cytoplasmic calcium concentrations in the cloned murine mast cell, MC9, have been measured using the fluorescent calcium indicator quin 2. Con A causes a rapid, small yet sustained rise in free cytosolic calcium (up to 245 nM) followed closely by increased 45calcium uptake and more slowly by histamine release. The increases in 45calcium uptake and histamine release require extracellular calcium. However, the Ca2+ influx blockers, nifedipine and verapamil inhibit these responses only at concentrations significantly higher than those used in smooth muscle to oppose potential-dependent events, and diltiazem is inactive. These observations suggest that, in these mast cells, other types of channels control Ca2+ entry. In contrast, the intracellular Ca2+ blocker, TMB-8, inhibits both the Con A-induced histamine release and the Ca2+ changes. The calmodulin antagonists calmidazolium, trifluoperazine and W-7 are also highly effective inhibitors of both the Ca2+ changes and histamine release in direct proportion to their potency against calmodulin-dependent phosphodiesterase, implicating calmodulin in the regulation of stimulus-secretion in MC9 cells. These data imply that histamine release follows increases in intracellular Ca2+ concentration. Free intracellular Ca2+ results from rapid release from internal stores and is followed by a slower but more sustained influx of extracellular Ca2+.

Antiallergic activity of loratadine, a non-sedating antihistamine.

Loratadine is a new non-sedating antihistamine. The present studies compared loratadine and terfenadine, another non-sedating antihistamine, for their ability to inhibit the bronchial response to histamine and other autacoids which have been implicated as contributing to the symptoms of an allergic reaction. In addition, the two antihistamines were evaluated in models of immunologically mediated allergic reactions. Loratadine is a more potent inhibitor of histamine-induced bronchospasm in guinea pigs than is terfenadine. Both antihistamines exhibit marked antiserotonin activity at doses 10 times their antihistamine ED50 values. In contrast, loratadine and terfenadine produce little or no inhibition of the bronchial responses to methacholine, leukotriene C4 or platelet-activating factor. An allergic bronchospasm in guinea pigs is inhibited by loratadine (ED50 = 0.40 mg/kg, p.o.) and terfenadine (ED50 = 1.7 mg/kg, p.o.). The bronchospasm associated with allergic anaphylaxis in rats is significantly inhibited by 10 mg/kg, p.o. loratadine and 30 mg/kg, p.o. terfenadine. Loratadine exhibits antiallergy activity in vitro. At micromolar concentrations, loratadine inhibits the release of histamine from Con A and A23187-stimulated rat peritoneal mast cells and the release of histamine and leukotriene C4 from a Con A-stimulated cloned murine mast cell line.

Bronchodilator and antiallergy activity of forskolin.

Forskolin is a diterpene from the roots of Coleus forskohli which directly activates the adenylate cyclase and raises cyclic AMP levels in a variety of tissues. Forskolin was studied for its effects on the tone of airway smooth muscle and the immunologic release of leukotrienes and histamine. The bronchospasm induced by inhaled antigen in sensitized guinea pigs was prevented in a dose-related fashion by the intravenous (i.v.) or intratracheal administration of forskolin. Forskolin was more potent than aminophylline and less potent than salbutamol. There was no evidence that forskolin would potentiate the in vivo bronchodilator effects of either salbutamol or aminophylline. Forskolin was approximately 100 times more potent than aminophylline by the i.v. and intratracheal routes to reverse an established allergic bronchospasm. Forskolin given intratracheally also inhibited the bronchospasm to i.v. histamine, with a short duration of action. In vitro forskolin (less than 1 microM) inhibited contractions of lung parenchyma provoked by histamine, LTC4 or antigen. Forskolin (1 microM) also inhibited the immunologically stimulated release of LTD4 and histamine from sensitized guinea pig lung. These studies show that forskolin shares with other agents that elevate cyclic AMP levels the ability to relax airway smooth muscle and inhibit mediator release in vitro and elicit a bronchodilation in vivo.

Evaluation of the CNS properties of SCH 29851, a potential non-sedating antihistamine.

SCH 29851 [8-chloro[6,11-dihydro-11-(1-carboethoxy-4-piperidylidene)- 5-H-benzo [5,6]cyclohepta[1,2-b]-pyridine] was discovered as part of a search for a new antihistamine without effects on the central nervous system (CHS). Antihistaminic potency and duration of action of SCH 29851 and other antihistamines were assessed by inhibition of histamine-induced lethality in guinea pigs and histamine-induced paw edema in mice. Evaluation of possible CNS effects included gross observation of mice, rats, dogs and monkeys, prevention of electroshock-induced convulsions, acetic acid-induced writhing and physostigmine-induced lethality in mice and biochemical measures related to sedative liability such as displacement of in vivo 3H-mepyramine binding in mouse brain and in vitro 3H-WB 4101 binding in guinea pig cortex. Comparisons were made to several antihistamines considered to be sedative to varying degrees, including diphenhydramine, promethazine, chlorpheniramine and azatadine and to the newer antihistamines terfenadine and astemizole which are reported to be non-sedating in man at doses that antagonize the effects of histamine peripherally. SCH 29851 had antihistamine activity in the tests used with a potency at least comparable to most standards and was devoid of activity in all the functional and biochemical models used as indices of CNS activity. It is expected that SCH 29851 should be an effective, long acting, antihistamine in man without sedative effects at therapeutic doses.

Hamster flank organ hydrolase and lipase activity.

The hydrolase and lipase activities of homogenates of the golden Syrian hamster flank organ (sebaceous complex) and skin were studied using synthetic fluorogenic substrates, 4-methylumbelliferone butyrate (4 MUB) or 4-methylumbelliferone palmitate (4 MUP). Homogenates of both flank organ and skin demonstrate a higher level of hydrolase activity (MUB substrate) than lipase activity. Flank organ however is enriched in lipase activity (4 MUP substrate) demonstrating 8 times as much activity as the skin. Systemic androgen treatment of female hamsters significantly stimulates the flank lipase activity while topical estradiol or the antiandrogen flutamide significantly decrease lipase. Testosterone and estradiol have a converse and weaker influence on hydrolase activity suggesting that this activity may be associated with different cell types. These effects do not appear to be direct since these compounds do not inhibit either enzyme in vitro. This data suggests a role for endogenous tissue lipases in the maturation of sebaceous tissue. Tetracycline and retinoic acid inhibit the activity of both enzymes in vitro. Retinoic acid also inhibited both in vivo while tetracycline inhibited only the lipase.